Autosensing LMI protocols in frame relay networks

ABSTRACT

The invention provides a method and system for auto-sensing LMI protocols in frame relay networks. When a router is first coupled to a frame relay network, it automatically configures the local management interface (LMI) to use one of a selected set of possible LMI protocols, by generating a set of protocol requests for a plurality of protocols, and by thereafter simultaneously listening for protocol responses from the configuration server. Multiple valid responses from the configuration server are assigned priority in response to which valid response is last to arrive.

This application is a continuation, pursuant to 35 U.S.C. Section 120,of prior U.S. Pat. application Ser. No. 09/140,178 entitled “AUTOSENSINGLMI PROTOCOLS IN FRAME RELAY NETWORKS,” by Fowler et al., filed on Aug.25, 1998, now U.S. Pat. No. 6,434,120 which is a continuation of U.S.Pat. Application Ser. No. 08/672,674 entitled “AUTOSENSING LMI PROTOCOLSIN FRAME RELAY NETWORKS,” by Fowler et al., filed on Jun. 28, 1996 nowU.S. Pat. No. 5,802,042.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to autosensing LMI protocols in frame relaynetworks.

2. Description of Related Art

Frame relay networks include a number of remote stations, each coupledto another; one node may be designated as a server node. When the numberof remote stations is large, or if the remote station is geographicallyremote, it can be difficult to assure that remote stations are properlyconfigured for use with the network, due in part to lack of technicalresources. One aspect of properly configuring the remote station is toassure that it uses the correct one of multiple possible protocols forthe local management interface (LMI) for the connection between theremote station and an edge of the frame relay network at a frame relayswitch; these possible protocols are called LMI protocols.

In one system for automated configuration of a remote station, theremote station attempts to communicate with frame relay networkequipment using a series of LMI protocols, each tested in sequence.While this technique achieves the goal of sensing LMI protocols, it hasthe drawbacks of taking more time than necessary, and of predeterminingan order for selection of an LMI protocol which may not ultimately bepreferred.

Accordingly, it would be advantageous to provide an improved techniquefor autosensing LMI protocols in frame relay networks.

SUMMARY OF THE INVENTION

The invention provides a method and system for auto-sensing LMIprotocols in frame relay networks. When a router (or other clientprocess) is first coupled to a frame relay network, it automaticallyconfigures the local management interface (LMI) to use one of a selectedset of possible LMI protocols, by generating a set of protocol requestsfor a plurality of protocols, and by thereafter simultaneously listeningfor protocol responses from the frame relay network equipment or switch.In a preferred embodiment, multiple valid responses from the frame relaynetwork equipment are assigned priority in response to which validresponse is last to arrive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a method of autosensing LMI protocols in frame relaynetworks.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description, a preferred embodiment of the invention isdescribed with regard to preferred process steps and data structures.However, those skilled in the art would recognize, after perusal of thisapplication, that embodiments of the invention may be implemented usinga computer at each site operating under program control, and thatmodification of a set of general purpose computers to implement theprocess steps and data structures described herein would not requireundue invention.

Autosensing LMI Protocols in Frame Relay Networks

FIG. 1 shows a method of autosensing LMI protocols in frame relaynetworks.

A method 100 of autosensing LMI protocols is performed in a frame relaynetwork.

At a flow point 110, a new router has been added to a frame relaynetwork.

In a preferred embodiment this method is performed for a new routerbeing added to a frame relay network and downloading configurationinformation from a configuration server on the frame relay network.However, in alternative embodiments, the method may be performed for anyclient process which is establishing or re-establishing contact with aserver process.

At a step 121, the router is powered up and attempts to contact theframe relay network equipment or switch.

At a step 122, the router transmits a “STATUS ENQUIRY” message using afirst LMI (local management interface) protocol. In a preferredembodiment, this first LMI protocol is the “ANSI” protocol, as describedin “Integrated Services Digital Network (ISDN)—Signaling Specificationfor Frame Relay Bearer Service for Digital Subscriber Signaling SystemNumber 1 (DSS1)”, ANSI Document T1.617-1991, Annex D, herebyincorporated by reference as if fully set forth herein.

At a step 123, after transmitting the message, the router sets a timeoutfor a response to that message, and starts a timer interrupt to occur onthat timeout. This timeout is preferably set for T391 seconds; the T391timeout is described on page 75, table D.2, of ANSI DocumentT1.617-1991, and is preferably between about 5 to about 30 seconds, suchas about 10 seconds. The router listens on LMI management channel numberzero (0) for a response.

At a step 124, the router transmits a “STATUS ENQUIRY” message using asecond LMI (local management interface) protocol. In a preferredembodiment, this second LMI protocol is the “ITU” protocol, as describedin “International Telegraph and Telephone Consultative Committee—DigitalSubscriber Signaling System No. 1 (DSS1). Signaling Specification forFrame Mode Basic Call Control, CCITT Document Q.933, 1992, herebyincorporated by reference as if fully set forth herein.

At a step 125, after transmitting the message, the router sets a timeoutfor a response to that message, and starts a timer interrupt to occur onthat timeout. This timeout is preferably set for T391 seconds. Therouter listens on LMI management channel number zero (0) for a response.

At a step 126, the router transmits a “STATUS ENQUIRY” message using athird LMI (local management interface) protocol. In a preferredembodiment, this third LMI protocol is the LMI protocol described in“Frame Relay Specification with Extensions—Based on Proposed T1S1Standards”, Document Number 001-208966, Revision 1.0 (Sep. 18, 1990),sometimes called the “gang of four” protocol and herein called the “LMI”protocol, hereby incorporated by reference as if fully set forth herein.

At a step 127, after transmitting the message, the router sets a timeoutfor a response to that message, and starts a timer interrupt to occur onthat timeout. This timeout is preferably set for nT1 seconds; the nT1timeout is described on page 6–12 of Document Number 001-208966, and ispreferably between about 5 to about 30 seconds, such as about 10seconds. The router listens on LMI management channel number 1023 for aresponse.

Although in a preferred embodiment the router transmits the “STATUSENQUIRY” message using LMI protocols in the order described for thesteps 122, 124, and 126, in alternative embodiments it would be possibleto use a different order in which the messages are sent, a differentnumber of LMI protocols to test, or a different set of LMI protocols fortest.

Although in a preferred embodiment the timeouts are set for the valuesdescribed for the steps 123, 125, and 127, in alternative embodiments itwould be possible to use a different set of values for the timeouts.Moreover, although in a preferred embodiment the timeouts are set usingmultiple timer interrupts, in alternative embodiments it would bepossible to use other techniques for setting and catching timeouts, suchas a single timeout for all three messages, or a non-interrupt-basedtechnique.

At a flow point 130, the frame relay network equipment is ready toreceive a “STATUS ENQUIRY” message, and the router is listening forresponses to one or more of the “STATUS ENQUIRY” messages.

At a step 131, the frame relay network equipment listens for a “STATUSENQUIRY” message. The frame relay network equipment sets a timeout forreceiving that message, and starts a timer interrupt to occur on thattimeout. This timeout is preferably set for nT2 or T392 seconds (fromthe frame relay network equipment's perspective), such as about 15seconds, as described in ANSI Document T1.617-1991 and in DocumentNumber 001-208966. When the timeout occurs, the method continues at theflow point 140.

At a step 132, the frame relay network equipment receives one of the“STATUS ENQUIRY” messages.

At a step 133, the frame relay network equipment determines if thereceived “STATUS ENQUIRY” message is for an LMI protocol it recognizes.If not, the frame relay network equipment continues to listen for a“STATUS ENQUIRY” message at the step 131. In a preferred embodiment, theframe relay network equipment logs an error event if the received“STATUS ENQUIRY” message is for an LMI protocol which it does notrecognize.

At a step 134, the frame relay network equipment responds to the “STATUSENQUIRY” message by transmitting a “STATUS” message on the appropriateLMI management channel. If the “STATUS ENQUIRY” message was for the ANSIprotocol, the frame relay network equipment transmits the “STATUS”message on LMI management channel zero; if the “STATUS ENQUIRY” messagewas for the ITU protocol, the frame relay network equipment transmitsthe “STATUS” message on LMI management channel zero; if the “STATUSENQUIRY” message was for the LMI protocol, the frame relay networkequipment transmits the “STATUS” message on LMI management channel 1023.

At a step 135, the frame relay network equipment should further respondto the “STATUS ENQUIRY” message by configuring itself to use the LMIprotocol associated with that message. In a preferred embodiment, theframe relay network equipment will so configure itself, but in the eventit does not, the process begins again in an attempt to deliver the“STATUS ENQUIRY” message and cause the frame relay network equipment toso configure itself.

The frame relay network equipment then continues with the step 131 toreceive any further “STATUS ENQUIRY” messages.

The steps 131 through 135 are performed in parallel with the steps 141through 142.

At a step 141, the router receives a “STATUS” message for one of the LMIprotocols.

At a step 142, the router determines which LMI protocol the “STATUS”message is for, and configures itself for that LMI protocol.

The router then continues with the step 141 to receive any further“STATUS” messages. The router catches any timeout interrupts for the“STATUS ENQUIRY” messages transmitted in the steps 122, 124, and 126,until all “STATUS ENQUIRY” messages have been responded to or have timedout. Thereafter, the method proceeds at the flow point 150.

At a flow point 150, the frame relay network equipment has received atleast one “STATUS ENQUIRY” message from the router, and the router hasreceived at least one “STATUS” message in response thereto.

If the frame relay network equipment has only recognized one LMIprotocol, it has responded to the “STATUS ENQUIRY” message for that LMIprotocol only, and the router has therefore received only one “STATUS”message. The router and frame relay network equipment have thereforeconfigured themselves for that one LMI protocol only.

If the frame relay network equipment has recognized more than one LMIprotocol, it has responded to the “STATUS ENQUIRY” message for each ofthose LMI protocols, and has configured itself for each such LMIprotocol in turn. Similarly, the router has received one “STATUS”message for each such LMI protocol, and has configured itself for eachsuch LMI protocol in turn. The router and frame relay network equipmenthave therefore configured themselves for each LMI protocol seriatum; atthe flow point 150 they are therefore configured for the same LMIprotocol.

Although in a preferred embodiment, the router and frame relay networkequipment mutually configure to the last LMI protocol which is mutuallyrecognized, in alternative embodiments it would be possible for therouter and frame relay network equipment to mutually configure toanother mutually recognized. For example, the frame relay networkequipment could respond to the first “STATUS ENQUIRY” message only, andreject all others; the router would then receive only one “STATUS”message in response, and the router and frame relay network equipmentwould mutually configure to the LMI protocol for that first “STATUSENQUIRY” message.

The router and frame relay network equipment thereafter communicateusing the selected LMI protocol.

ALTERNATIVE EMBODIMENTS

Although preferred embodiments are disclosed herein, many variations arepossible which remain within the concept, scope, and spirit of theinvention, and these variations would become clear to those skilled inthe art after perusal of this application.

1. A method for performing auto-sensing of protocols used forcommunicating between entities of a data network, the method comprising:transmitting, from a first router, a plurality of requests, one for eachof a set of LMI protocols, to at least one other network device;receiving at least one response to at least one of said plurality ofrequests; identifying at least one LMI protocol associated with the atleast one response; and automatically configuring the router to utilizesaid at least one LMI protocol in response to said at least oneresponse.
 2. The method of claim 1 wherein the at least one othernetwork device includes a network device coupled to a frame relaynetwork.
 3. The method of claim 1 further comprising: identifying afirst LMI protocol associated with a first response of said at least oneresponse; automatically configuring the router to utilize said first LMIprotocol; identifying a second LMI protocol associated with a secondresponse of said at least one response; and automatically configuringthe router to utilize said second LMI protocol.
 4. The method of claim 1wherein the transmitting of the plurality of requests occurssubstantially simultaneously.
 5. The method as in claim 1, furthercomprising initialing a timeout for at least one of said plurality ofrequests.
 6. The method as in claim 1, further comprising initiating aseparate timeout for each one of said plurality of requests.
 7. Themethod as in claim 1, wherein said set of LMI protocols comprise an ANSIprotocol, an ITU protocol, and an LMI protocol.
 8. The method as inclaim 1 further comprising listening on a plurality of LIVE managementchannels for said at least one response; and receiving at least oneresponse on at least one of said plurality of LMI management channels.9. The method as in claim 8, wherein said plurality of LMI managementchannels comprises LMI management channels zero and 1023.